The invention relates to a structural piece used in combination with other structural pieces to form the ceramic tile floor of a shower or similar bathroom structure.
In wood-frame construction, ceramic tile shower floors are typically formed by first putting a moisture barrier over a wooden subfloor after which a mortar bed is sloped to the position of the drain, typically referred to as sloped fill, or “pre-slope.” A waterproof barrier, commonly referred to as a shower pan liner, is subsequently positioned over the sloped mortar bed and fixed to the drain. Conventional shower pan liners are not designed to bond to a substrate or to ceramic or stone tile and thus a second “floating” (non-bonded) mortar bed must be overlaid to provide a load distribution layer and bonding surface for the tile. To have sufficient strength, such non-bonded mortar beds for shower floors should have a minimum thickness (typically 1.5 inches) and should be reinforced with galvanized wire mesh to comply with industry standard guidelines.
Most such shower floors are sloped, and typically at a value of one-quarter inch (¼″) per foot. As a result, the position of the drain, the desired slope, and the length of sloped tile, all combine to define a height difference between the drain and the floor's perimeter (e.g., a wall, a curb, or a barrier-free entry).
This method of shower floor construction has proven over time to be reliable when properly built, but requires a high degree of trade knowledge and skill, and takes considerable time.
For a number of reasons, including consumer preferences, a desired increase in construction simplicity, and (in some cases) the unavailability of craftsmen who can carry out the conventional methods, the industry is moving toward simplified construction systems and methods, and toward simpler, cleaner and “open look” interior spaces. One trend is toward low profile shower curbs and toward eliminating perimeter curbs entirely.
To facilitate these trends, integrated systems have recently been developed that use lighter materials, and simplified installation methods that make lower profile shower floor construction both possible and less time-consuming. Much of this progress has been made possible with the advent of a new generation of materials that allow each layer of the structure to be bonded to the adjacent layer(s). In some cases these systems include a prefabricated shower bed tray (typically formed of polymer foam) which is mortar bonded to the subfloor. In some systems, a mortar bondable waterproofing membrane is fixed to the foam tray with thin set mortar. The tile is then bonded over the membrane, again using thin set mortar. Thus, a typical integrated system could include (in order) substrate/initial mortar layer/shower tray/second mortar layer/membrane/third mortar layer/tile.
As an additional consideration, the shower tray and its surrounding area must be flush with one another so that a level layer of tile can be placed upon it. To the extent that the shower tray is relatively thick at its perimeter, the surrounding areas must likewise be built up to match the tray perimeter. At the same time, the physical nature of the polymer foam tends to establish about one-half inch (0.5″) as the minimum thickness of the foam tray anywhere—including its thinnest portions at the drain.
As a result, the half-inch thickness of the tray at the drain must increase toward the perimeter to provide the ¼″ per foot slope. In turn, any area surrounding the tray perimeter must be made thicker to remain flush with the tray perimeter.
Thus, a thinner tray perimeter is desired, but this goal is limited (or in some cases frustrated) by the necessary thickness for the tray at the drain.
At the position where the shower drain is required, the flooring structure, including the shower tray and related portions of the integrated system, must be sufficiently strong to support the drain while still allowing the tile to be placed over the nearby foam tray and around the drain. Conventionally, this has required a relatively thick tray or relatively thick mortar, either of which in turn adds to the thickness of the overall floor structure and affects its relative height compared to the remainder of the area. Such additional thickness can be disadvantageous in many circumstances, including barrier-free shower enclosures (i.e., without any curbing).
In “fitting” a barrier free-construction within the thickness of typical subfloor panels, it is relatively easy to recess the subfloor panels in the footprint of the shower floor such that they are flush with the tops of the floor joists and without damaging those joists. The harder task is to compensate for the height difference between the recessed subfloor panels in the footprint of the shower floor and the adjacent subfloor (typically 0.75 inches).
Conventional shower floor constructions, and even the newer “integrated systems”, are often too tall (e.g., too thick) to “fit” within a ¾″-thick subfloor panel. Obtaining a flush, barrier free entry thus requires one or more of the following options: cutting or notching the framing members (which typically is a building code violation), having a very tall threshold at the entrance to the bathroom as a result of building up the floor adjacent to the shower floor to make it flush with the shower floor; ramping up to and around the shower floor; or providing an “engineered” solution such as cutting and heading off the joists in the area of the shower floor and subsequently lowering the subfloor/framing structure in the area of the shower floor. Such engineered solutions require extensive work, are costly and, in most cases, must be included in the design phase of the house. For practical reasons, this excludes most remodels and retrofits.
As a result, conventional shower floor constructions, including the newer “integrated systems” are taller (thicker) to provide support for the assembly or, in the case of the newer “integrated systems,” the drain.